KEF REFERENCE SERIES MODEL 105
Model 105 is the newest additionto the wellknown Reference Series based on KEF's experience in the production of high-grade monitoring loudspeakers for sound and television broadcasting organisations. Its design is the result of a long-term development aimed primarily at avoiding the restrictions - particularly in stereo reproduction - imposed by the directional characteristics of conventional loudspeakers.
Although the project involved some advanced mathematical theory, the design objective was a very practical one, namely, that the high standard of sound quality and stereo realism to be achieved should not be confined to some preferred listening position, but should be maintained constant over a defined area large enough to accommodate a group of listeners.
Judging by the outward appearance of Model 105, the most striking feature is the arrangement of the three drive units, two of which are mounted in a separate housing of somewhat unconventional shape. But this is only one aspect of a comprehensive development, in which drive units, filter networks, enclosures and spatial acoustic were all considered as part of an overall system-engineering plan.
Digital computer evaluation played a major role in the design of this loudspeaker system. By carefully matching the components drive units, enclosures and electronic dividing networks their overall combined acoustic performance is as near as possible to the theoretical ideal target response. Model 105 represents the finest achievements in modern loudspeaker technology.
All three drive units are housed in their own specially contoured enclosures, whose volumes and shapes match the frequency ranges they handle.the drive units are also staggered, so that thier effective sound path to the listeners ears are equal, to eliminate inter unit time delays. The result is extraordinary dispersion characteristics providing a broad and deep listening area within which the stereo definition and depth perspective have to be heard to be believed.
This ideal listening area in which Model 105 gives its designed response is visually identified for the listener. Furthermore the position of the area can be altered, within fixed limits by tilting and rotating the mid and high enclosures. Fuses protect the mid and high drive units, and a LED indicates the amplifier clipping.
Dimensions: 965 x 415 x 455 mm (38 x 16,3 x 17,9 in.)
Weight: 38 kg (80 lb)
300 mm (12") low-frequency unit with 50mm(2") high-temperature voice coil. Visco-elastic damped Bextrene diaphragm with PVC surround.
110 mm (5") middle-frequency unit with 25 mm (1") high-temperayure voice coil. Visco-elastic damped Bextrene diaphragm with PVC roll surround.
50 mm (2") high-frequency unit with 38 mm (1,5") voice coil. Mylar domed diaphragm with integral damped roll Surround.
low-frequency enclosure, 70 litres ; middle-frequency enclosures, 7 liters
Crossover frequencies: 400 Hz and 2500 Hz
Nominal impedance: 8 ohms
Programme rating: 200 watts
86 dB spl at 1 m on axis for 1 watt (anechoic conditions)
Max. continuos sinusoidal input:
35 V rms, 100 Hz to 400 Hz
28 V rms, 400 Hz to 2500 Hz
11 V rms, 2500 Hz to 20000 Hz
107 dB spl on programme peaks under typical listening conditions
Frequency response: 38 Hz to 22000 Hz ±2 dB at 2 m on axis
Horizontal, within ±2 dB of axial response up to 13000 Hz for ±20⁰;
Vertical, within ±1 dB of axial response up to 20000 Hz for ±5⁰
Peak level indicator:
Switchable (a) to indicate power levels of 40, 50, 60, 80, 100, 125, 150 and 200 watts, (b) to operate at low power levels while orientation of head assembly is being adjusted